Really good for live!
I fell in love with the 900 series from Sennheiser a year ago. This mic is amazing in live on the guitar amp, it will give you a really precise sound that you can dream getting with a 57. In the studio it's not the best, I prefer a warmer sound, but I found out you can get a better sound moving the mic some cm away from the amp, so don't use it too much close to the speaker in the studio. The design is really compact and it will make the difference in really small stages where with an amp clamp it will take just 3 cm of space to mic an amp.